Fuel injectors are used to deliver fuel to a combustion chamber of an engine. In many cases, these fuel injectors have high fuel pressure within that would be provided from a pump and rail arrangement located upstream of the fuel injectors. This high pressure of the fuel combined with an inter-relative geometry of a sac region and a needle tip of the fuel injector may influence one or more parameters associated with discharge and combustion of the fuel. These parameters in turn, affect the quality of emissions before being released into the atmosphere. For instance, during a fuel discharge event, many conventional fuel injectors have been known to dribble fuel to at least about a droplet size from their sac regions into the combustion chamber of the engine. This could lead to undesired effects including, amongst other things, the presence of unburned hydrocarbons in the emissions released by the combustion chamber.
Many strategies have been developed to reduce this dribble effect so that the quality of emissions from combustion chambers of an engine can be improved. One such strategy is disclosed in PCT Publication WO 1992/019859 (hereinafter referred to as ‘the '859 publication’). The '859 publication discloses a fuel injection nozzle having a nozzle body in which is formed a bore having a seating defined at one end. A valve member is movable in the bore and is shaped to cooperate with the seating to control fuel flow into a sac volume defined by a blind drilling formed in the body. Outlet orifices extend to an exterior of the body from the drilling and in order to reduce the volume of the sac volume an insert is positioned in the drilling. However, this insert may be displaceable in position when subject to extreme working pressures typically encountered in fuel injection nozzles. Moreover, due to a possibility of displacement in position of the insert, the body, and in particular, the sac region of the injection nozzle may be subject to collisions or abrasion from the insert thereby reducing a service life of the injection nozzle.
Hence, there is a need for a fuel injector having a sac region that is capable of withstanding high operational forces while also being configured to minimize fuel dribble from occurring during or after a fuel discharge event.